Hydraulic drive system



Nov. 10, 1953 s. BANISTER EI'AL HYDRAULIC DRIVE SYSTEM 4 Sheets-Sheet 1 Filed May 29, 1951 [171 517 far Nov. 10, 1953 v G. BANISTER ETAL' 2,558,342

HY DRAULI C DR IVE SYSTEM Filed May 29, 1951 4 Sheets-Sheet 2 Patented Nov. 10, 1953 nvnmuuo DRIVE SYSTEM Guy Banister and Leonard Stephen Burns,

Aurora, 111.; assignors to Barber-Greene Company, Aurora, 111., a corporation of Illinois ApplicationMay 29, 1951, Serial No. 228,812

Claims.

This invention relates to a hydraulic drive system and more particularly to a hydraulic control system for one or more hydraulic motors which is adapted for various applications.

An object of this invention is'to provide an improved control system for .a hyd ulic m t rin which an adjustable Valve is provided for by- Passing a portion of th fluid under pressure supplied to the motor, the fluid flow to the motor being continuously variable W thin limits by a justment of the valve.

Another object of this invention is to provide an p ved control ystem for a p ur lity of y ul ,.motors utilizing a mum-valved and passaged unit, the unitfhavlng a relief valve incorporated therein for limiting the fluid pressure su plied to the motors.

A further object ofthis invention is to provide an improved control system for a pair of hydraulic motors in which a multi-valved and passaged unit has a separat ontrol for ea h of the motors, the fluid flow to .one or the motors being blocked off when the control to; the other motor is in a feed position.

Still another object of this invention is to pro.- vide an improved control systemfor a hydraulic motor in which a control may be set for either forward or reverse operationof the motor and in which means are provided for adjusting the forward speed of the motor, the speed adjustment means being inoperable in the reverse set-. ting of the control.

A still further object of this invention is to provide an improved control system for any draulic motor in which a valve controls fluid flow to the motor, the control valve being selectively operable to forward and reverse positions and to a neutral position in which fluid conduits to the motor are blocked off so that the motor may act as a brake.

The hydraulic drive system of this invention includes a pair of hydraulic motors and control means therefor. The motors may be used in any machine or for anyapplication where actuation of elements inter-related in operation is desired. The motors may he ofany desired type, having either rcciprocable or rotatable fluid actuated elements. It will, of course, be understood that the principles of this invention can be applied to hydraulic drive systems using any number of motors. t

The hydraulic system includes a ,fluidreservoir, a pump and a multi-va lved andpassaged unit having a separatev controlforeach of the hydraulic motors. important feature of this invention is in the provision of a valve for bypassing fiuid. from the motor, the valve being adjustable sothat the speed of the motor may be adjusted with infinite possible variations within the motors is selectively movable to forward,

reverse and neutral positions. In the forward position of the control, the by-pass valve is operable for controlling the speed of the motor whilein the reverse position of the control, the by-pass valve is inoperable so that the speed in reverse is fixed regardless of the adjusted setting of the by-pass valve. Also, with the control in the neutral position, the conduits to the motor are blocked on so that the motor may act as a brake.

Other objects, features and advantages of the present invention will become more fully apparent from the following detailed description taken in conjunction with the accompanying drawings which illustrate a preferred embodi merit of the invention and in which:

Figure 1 is a view illustrating diagrammatically the hydraulic drive system of the present invention including hydraulic motors, a pump, a reservoir and a control unit;

Figure 2 is a view illustrating diagrammatically the fiow'in the hydraulic system with the controls for both hydraulic motors in neutral positions;

Figure 3 is a view illustrating diagrammatically the flow through the hydraulic system with the control for one motor in a. neutral position and with the control for the'other motor in a reverse position;

Figure 4 is a view similar to Figures 2 and '3 illustrating the flow in the hydraulic system with the control for one motor in a neutral position and the control for the other motor in a forward feed position;

Figure 5 is aview illustratingthe flow with the controls in the same position as Figure 4 except that the by-pass valve is open for adjustment of the forward speed of the one motor;

Figure 6 is a view illustrating diagrammatically the flow in the hydraulic system with one control in a feed position and the other control ma neutral position, this view also illustrating flow through the relief valve incorporated in the control-unit;

Figure 7 is a view illustrating diagrammath cally the flow in the hydraulic system with one control in a retract position and with the other 3 control in the forward feed position and with by-pass valve adjusted to be at least partially open to reduce the speed of the motor;

Figure 8 is a top plan view of the control valve unit;

Figure 9 is a sectional view, on an enlarged scale, taken substantially along lines IX-IX of Figure 8;

Figure 10 is a sectional view, on an enlarged scale, taken substantially along lines X-X of Figure 8;

Figure 11 is a sectional view, on an enlarged scale, taken substantially along lines XI-XI of Figure 8; and

Figure 12 is a sectional view taken substantially along lines XII-XII of Figure 11.

Referring to Figure 1, the hydraulic drive system of this invention may include a pair of hydraulic motors generally designated by reference numerals and 2|. The hydraulic motor 20 herein comprises a cylinder 22 and a piston 23 reciprocably movable in the cylinder. Means, not shown, are preferably provided for biasing the piston 23 upwardly. The hydraulic motor 2| is herein a reversible rotating type having an output shaft 24. It will be understood that either of the motors 28 and 2| may be either a reciprocable type or a rotating type. It will be further understood that the principles of this invention can be applied to any number of hydraulic motors in a drive system.

The hydraulic motors 28 and 2| may be used to actuate elements in any desired apparatus. By way of example, the motors may be used in a ditching machine wherein the hydraulic motor 28 may be used to control the raising and the lowering of a boom carrying a digging bucket line thereon and the hydraulic motor 2| may be used to actuate the traction means of the digging machine.

The hydraulic system which actuates the hydraulic motors 20 and 2| includes a fluid reservoir or tank 25, an engine-driven pump 26 and a control unit generally designated by reference numeral 21. The construction of the control unit 21 will be described in detail hereinafter, but in general, it is a multi-valved and passaged unit having a lever 28 controlling the hydraulic motor 28 and a lever 29 controlling the hydraulic motor 2|.

The inlet side of the pump 26 is connected to the reservoir 25 through a strainer 3|. The out let side of the pump 26 is connected to the control unit 21 through a conduit 32. The upper end of the cylinder 22 is connected to the control unit 21 through a conduit 33 and the lower end of the cylinder 22 is connected to the reservoir 25 through a conduit 34. The hydraulic motor 2| is connected to the control unit 21 through a pair of conduits and 36. An adjustable valve 31 is provided for by-passing fluid from the hydraulic motor 2| in one position of the control lever 29. The by-pass valve 31 is connected to the control unit 21 through a pair of conduits 38 and 39 and is connected to the reservoir 25 through a conduit 48. A conduit 4| is connected to the control unit 21 and joins the conduit for flow of fluid from the control unit 21 to the reservoir 25.

Figures 2, 3, 4, 5, 6 and 7 illustrate diagrammatically the flow in the hydraulic system in various positions of the control levers 28 and 29 of the control unit 21.

Figure 2 illustrates the flow when the control levers 28 and 29 are both in neutral positions. This flow will be from the pump 26 through con- '4 duit 32 to the control unit 21 and out through conduits 4| and 48 to the reservoir 25.

Figure 3 illustrates the flow when the control lever 28 is in a neutral position and the control lever 29 is in a reverse feed position. This flow will be from the pump 26 through conduit 32 to the control valve unit 21, out through conduit 38 to the hydraulic motor 2|, back through conduit 35 to the control unit 21, out through conduit 4|, and back through conduit 40 to the reservoir tank 25.

Figure 4 illustrates the flow with the control lever 28 in neutral position, the control lever 29 in a forward feed position and with the by-pass valve 31 closed. This flow will be from the pump 26 through conduit 32 to the control unit 21, out through conduit 38, back through conduit 39 to the control unit 21, out through conduit 35 to the hydraulic motor 2|-,- back through conduit 36 to the control unit 21, out through conduit 4|, and back through conduit 48 to the reservoir tank 25.

Figure 5 illustrates the flow of the hydraulic system with the control lever 28 in neutral position, the control lever 29 in forward feed position and with the by-pass valve 31 at least partially open, that is, with the levers 28 and 29 in the same position as in Figure 4 but with the by-pass valve 31 at least partially open. This flow will be from the pump 26 through conduit 32 to the control unit 21, out through conduit 38 where the flow divides, a portion of the flow being through the by-pass valve 31 back through conduit 48 to the reservoir tank 25 and the remaining portion of the flow being back through conduit 39 to the control unit 21, out through conduit 35 to the hydraulic motor 2|, back through conduit 36 to the control unit 21, out through conduit 4|, and back through conduit 48 to the reservoir tank 25.

It will be noted that with the levers 28 and 29 in the positions of Figures 4 and 5, the flow through the conduits 35 and 36 which feed the hydraulic motor 2| will be the reverse of the flow through conduits 35 and 36 in the position of the levers of Figure 3. It may also be noted that the by-pass valve 31 may be adjusted to control the fluid pressure applied to the hydraulic motor 2|, and hence the speed of the motor. In the reverse feed position of the lever 29 as illustrated in Figure 3, however, the by-pass valve 31 will be blocked off so that the full output pressure of the pump 26 will be applied to the hydraulic motor 2| and the motor operated at full speed reverse regardless of the setting of by-pass valve Figure 6 illustrates the how in the hydraulic system with the lever 28 in feed position and with the lever 29 in neutral position. In this position of the controls, fluid will flow from the pump 26 through conduit 32 to the control unit 21 and out through conduit 33 to the upper portion of the cylinder 22 to urge the piston 23 downwardly against a biasing force preferably acting thereon. Fluid in the lower portion of the cylinder 22 may, of course, flow through the conduit 34 to the reservoir tank 25. Figure 6 also illustrates flow that may take place through a relief valve in the control unit 21 out through conduit 4| and back through conduit 48 to the tank 25. This flow will take place whenever the fluid pressure from the pump 26 exceeds a predetermined value and may, for example, take place when the movement of the piston 23 is blocked.

Figure 7 illustrates the flow in the hydraulic measure system when the lever is in a retract position and also illustrates the flow that may take place with the lever 19 in :rorwaru feed position. In

this positionof the control lever 28, the piston 23 may be moved upwardly by a biasing force to force fluid from the'upper portion of the cylinder 22 through the conduit 33 to the control unit '21, out through conduit 4| and back through conduit 40 to the tank 25. Simultaneously, fluid may flow fr'o'm the pump 26 through conduit 38 to a zjodiiit where the flow divides, a portion of the flow being through the by-pass valve .31 and back through conduit 40 to the tank 25 and the remaining portion of the flow back through con drift 39 to the control unit 21, out through conduit to the motor 2|, back through conduit '35 to the control unit 21, 'out through conduit 4| and back through conduit 40 to the tank '25. It may be noted that with the lever 28 in the retract position, as in Figure 7, the motor 2| may be-actuated, butwhen the lever 28 is in the feed position, in 'Figure 6, the motor 2| is blocked off and cannot be actuated.

The control unit 21 is illustrated in detail in Figures 8, 9, 10, 1 -1 and 12. Referring thereto, the'unit 21 includes a pair'of end caps-44 and 45 between which three valve body sections 46, 41 and 48 are disposed. The end caps 44 and 45 and the'valve body sections 46, 41 and 4B are secured in assembly by tie bolts "49 andnuts 50. The'as'sembly 2'1 maysbe'secured to a "portion 5| of the machine with which used by bolts or screws 52.

Three plunger's 55,54 and are slid'ably disposed in'the valveib'ody section 46, 41 and '48, respectively. The position of plunger 53 may be adjusted and controlled by the control lever 28 and the positions of .plun'gers 54'and '55 may be a-djusted'and controllediby the lev'er29. For this purpose a bracket 51 havingprojecting arm portions 51a, 51b and 510 is secured to the portion 5| by means of boltsor screws 58. The lever 28 is pivotally disposed on a pin I59 extending between the portions 51a and 51b of the bracket 51 and the end portion of the lever 28 is connected to the plunger 53 by means of a pair of linkst a :pin 62 extending through the links and the end portion of the lever 28 and a .pin 63erstending through the links 6| and the upperen-d portion of the plunger '53.

The lever 29 is bifurcated at its inner end to form spaced .parallel portions 64 and 65, the lever 29 being pivoted to the bracket51 by means of a pin 66 extending through the arm portions '51b and 510 andzthroug-h the inner end portions of the legs 64 and '65. The leg 64 is connected :to theplunger 54 by means-of a pair of links :61, a pin=58 securing the links to the leg 64 and a "pin '69 securing the links "58 to the upper portion of the plunger 54. It may be here noted that, as shown in Figure 11, "each link 61 has a longitudinal slot 51a through which the pin 68 extends so that a lost-motion connection is provided between the lever 29 and the plunger 54. This lost-motion connection is for a purpose which will appear hereinafter.

The leg '65 of the lever '29 is connected to the plunger 55 by means fora pair of links 1|,"a pin T2 securing the link 1| to the leg-55, and a-pin 13 securing the links 1| to the up er end portionof the plunger 55.

The plunger 53 is resiliently urged into the neutm position illustrated iniFigures 9 and 11. For this purpose-a hollow tan 15 is threaded into the lower end-or the valve-body section 45 and the chamber '89.

extends over the lower end portion of the plunger 53. A ring 16 is'disposed around the plunger .53 and is adapted to engage an annular abutment on the plunger 53 and an annular abutment .in the valve body section 46. A similar ring 11 is adapted to engage an annular abutment'on the plunger 53 and an annular abutment in the cap 15. Between the rings 16 and 11 is a helical compression spring 18 resiliently urging the ring 16 into-engagement with the annular abutments of the plunger 53 and valve body section 46, and the ring 11 into engagement with the annular abutments in the cap 15 and plunger 53.

It will be seen that theplunger 53 can'thus be moved up or-down 'againstthe action of the compression spring 18 and will be returned to the neutral position illustrated in Figures 9 and 11 when released.

Means are provided for locking the plunger 55 into any one of three selectedrpositions. A cap memberl'fl is threaded into the lower end of the valve body section 48 and extends over the lower end of the plunger 55. A spring-pressed ball detent is mounted inthe cap member 19 and 'is adapted to engage anyoneof three .vertically spaced annular grooves 8|, 82 and 83 in the lower end portion of the plunger :55 to lock the plunger in a selected -verticallposition.

Similar means are provided for locking the plunger 54 in either one of two selected positions. A cap member-84 .is threadedinto the lower ends of the valve body section 4:1. Mounted in the cap member 84 is a .springepressed ball detent (not shown) which is adaptedtoengage either of two vertically-spaced grooves 8-5 and 185 in the lower-end portion of the plunger 54. Onlyntwo annular grooves are provided in=the plunger 54 since, due to the lost -motionconnection between the lever 29 and the'plun'ger 54 described above, the plunger :54 will not be moved downwardly when the lever 29 is moved downwardly.

The end cap-=44 :hasanopening 88 into which the conduit 32 .from the pump .26 may beacon.- nected. The opening-88 extendsinto a'chamber .89 which thus has-fluid under zpressureiromthe pump 26 therein. The end cap 45 has-an-open ing 99 therein into which the conduit line =4| may be connected. Thi openin'g 9|! extends-into a chamber 9|.

The valve body section's, =41 and 48 have aligned openings-94therethrough (Figures Qand 10) which communicate with a passage in the end cap 44 and with the chamber 9| in the endcap 45. 'As-bestshowninlrigure l2, thepassage 95 in the end cap 44 communicates wi-th:a chamber 96 at one side of a spring-pressed zrelief valve member 91i .A passageiso-extendstrom the other side of the relief valve member .91 'to It will be readily seen that when the pressure from thepump 26 is sufiic'ient to overcome the spring pressure actingagainst the relief valve member -91, the /-fl-uid :can flow from the chamber 89 through the passage .93, past the relief valve 91 into the chamber -96, through the passage 95, through the aligned opening 94 in the three valve body "sections, to thechamber 9| inthe end -*cap45, out through the conduit 4|, and back through conduit-40 to the reservoir tank 25. The relief valve :91 thus prevents blocking of the pump and damage thereto.

The relief valve '91 also limits the pressure which may be applied to the hydraulic meters 20 and 2|. Th'is ishighly-advantageous in many applications-to which the hydraulic drive of 'this invention may be applied. For example, it the elements to which the piston 23 is connected in a particular machine are so designed that they cannot withstand more than a certain amount 01 actuating force, the relief valve 91 can be adjusted so that fluid pressure applied to the piston 23 is limited and so that the force applied by the piston 23 will not exceed the safe design limit.

Referring to Figures 9 and 11, the valve body section 46 has vertically spaced annular internal grooves IOI, I02, I03, I04 and I surrounding the plunger 53. The plunger 53 has portion I06 and I01 of reduced diameter which, together with the internal surfaces of the valve body section 46, form fluid flow passageways. The annular groove IOI communicates with a passage I09 extending to the valve body section 41. The annular groove I02 communicates with the chamber 89 in the end cap 44 through a passage IIO. A shown in Figure 9, the annular groove I03 communicates with the conduit 33 through a check valve including a spring-pressed ball III. The annular groove I04 communicates through a passage I I2 with the opening 94 which, as described above, communicates with the reservoir tank 25. The annular groove I05 communicates directly with the conduit 33 which is connected to the upper end of the hydraulic cylinder 22.

In the position of the plunger 53 illustrated in Figures 9 and 11, fluid may flow from the pump 26 through conduit 32 into the chamber 89 and from the chamber 89 through the passage IIO into the valve body section 46 and out through the passage I09 to the valve body section 41. The flow in the valve body sections 41 and 48 will control the operation of the hydraulic motor 2|, as will be described later.

When the plunger 53 is moved downwardly from the positions illustrated in Figures 9 and 11, the fluid flow will be as diagrammatically illustrated in Figure 6. Fluid under pressure from the pump will flow from the chamber 89 through the passage IIO into the grooves I02 and I03 in the valve body section 46, and from the groove I03 past the spring-pressed ball I II into the conduit 33 and to the upper portion or the cylinder 22 to force the piston 23 downwardly against the biasing force preferably acting upwardly thereon. In this downward position of the plunger 53 it will be noted that the annular internal groove I09 leading to the valve body section 41 will be closed off so that the hydraulic motor 2I cannot be actuated. This is highly advantageous in certain applications such as, for example, in machines where the hydraulic motor 2I drives the traction means and it is desired that the traction means be braked when the hydraulic motor 20 is actuated in one direction.

If the lever 28 is held up after the piston 23 has moved to the limit of its movement, fluid pressure building up in the chamber 89 will be released through the relief valve 91.

When the plunger 53 is moved upwardly from the neutral position illustrated in Figures 9 and 11, the piston 23 in the cylinder 22 will preferably be moved upwardly by a biasing force acting thereon and fluid will be forced out through the conduit 33 into the annular internal grooves I05 and I04, from groove I04 through the passage II2 into the opening 94, into the chamber 9I, out through the conduit H, and back through the conduit 40 to the reservoir tank 25.

It will be noted that in this upper position of 8 th plunger 53, fluid under pressure from the pump may flow from the chamber 89, through the passage I I0, and through the passage I08 through the valve body sections 41 and 48 so that the hydraulic motor 2| may be actuated. The flow through the control unit in this upper position of the plunger 53 is diagrammatically illustrated in Figure 7.

The fluid flow passages in the valve body sections 41 and 48 and in the plungers 54 and 55 are exactly the same, and for that reason a section (Figure has been taken only through the valve body section 48. Referring to Figures 10 and 11, the valve body section 48 has vertically spaced internal annular grooves H4, H5, H6, H1, H8, H9 and I around the plunger 55. The groove II4 communicates directly with the conduit 35 which extends to the hydraulic motor 2I. The annular groove II5 communicates through a passage I2I with the chamber 9I in the end cap 45. The annular groove II6 communicates with the conduit 35 through a check valve including a spring-pressed ball I22. The annular groove I I1 communicates through a passage I23 with the valve body section 41. The annular groove II8 communicates through a check valve, including a spring-pressed ball I24, with the conduit 36 which is connected to the hydraulic motor 2I. The internal annular groove II9 communicates through a passage I25 with the chamber III in the end cap 45. The annular groove I20 communicates directly with the conduit 36.

The plunger 55 has three vertically spaced reduced diameter portions which, together with opposing internal surface portions of the valve body section 48, form fluid flow passages. The plunger 55 also has an axially extending internal chamber I21 from which extends horizontal, vertically spaced passages I28, I29 and I30.

As indicated above, the fluid flow passages in the valve body section 41 and the plunger 54 are the same as those in the valve body section 48 and plunger 55. The valve body section 41 has vertically spaced internal annular grooves I32, I33, I34, I35, I36 and I31 around the plunger 54 which correspond with the internal grooves H4, H5, H6, H1, H9 and I20 oi. the valve body section 48.

The annular groove I32 communicates directly with the conduit 38 extending to the by-pass valve 31; the groove I33 communicates through a passage I with the passage I23 in the valve body section 48; the annular groove I34 communicates through a check valve (not shown) with the conduit 38 extending to the by-pass valve 31; the annular groove I35 communicates with the passage I09 in the valve body section 46; the annular groove I36 communicates through a passage I39 with the passage I23 in the valve body section 48; and the annular groove I31 communicates with the conduit 39 which extends to the by-pass valve 31.

The plunger 54 has an axially extending chamber I40 similar to the chamber I21 in the plunger 55. Extending from the chamber I40 are horizontal, vertically spaced passages I4I, I42 and I43 similar to the passages I28, I29 and I30 in the plunger 55.

In the neutral positions 01' plungers 53, 54 and 55 illustrated in th drawings, fluid will flow as diagrammatically illustrated in Figure 2. In this case, fluid under pressure from the pump 26 may flow from the chamber 89 through the passage I I0 in the valve body section 46, through the pasaesassa sage I03 through the valve body section 41. through passage I42 into the internal chamber I40 in the plunger 54, out through passages MI and I43 into passages I 38 and I39, respectively, in the valve body section 41, through passage I35 into the valve body section 48, through passage I29 into the internal chamber I2'I in the plunger 55, out through passages I28 and I30 to the passages HI and I25, respectively, to the chamber 9I in the end cap 45, out through conduit, and back through conduit 49 to the reservoir tank 25.

It will be noted that with the levers 25 and 29 in the neutral positions thereof, both hydraulic motors 29 and 2| will be blocked off and locked in position so as to act as brakes on elements that may be connected thereto.

When the lever 23 is in its neutral position and the lever 29 is moved downwardly, the fluid flow in the hydraulic system will be as diagrammatically illustrated in Figure 3. Due to the lostmotion connection between lever 29 and plunger 54, the plunger 54 will not be moved downwardly by downward movement of the lever 29, but the plunger 55 will be moved to its downward position.

In this position of the controls, the fluid flow in the valve body sections 46 and 41 will be as described above and fluid under pressure from the pump will flow through the passage I23 in the valve body section 48, into the annular grooves II! and II 8 and from the groove II 8 past the spring-pressed ball I24, out through conduit 36 to the hydraulic motor 2|, back through conduit 35 into the annular grooves H4 and H5, and from annular groove II5 through passage I2I into the chamber 9| in the end cap 45, out through conduit 4|, and back through conduit 40 to the reservoir tank 25.

It will be noted that in this downward or reverse feed position of th lever 29, the conduits 38 and 39 leading to the by-pass valve SI are blocked oif since the plunger 54 is in its neutral position. Thus, the hydraulic motor will have the full fluid pressure of the pump 26 applied thereto.

When the lever 28 is in its neutral position and the lever 29 is moved upwardly, both the plunger 54 and the plunger 55 will be moved upwardly. The fluid flow in this instance will be as diagrammatically illustrated in Figures 4 and 5. Since the plunger 53 is in a neutral position, fluid under pressure from the pump will appear at the passage I99 in the valve body section 46 and will flow into the grooves I35 and I 34 and from groove I 34 out past a check valve (not shown) to the conduit 38 toward the by-pass valve 31 where the flow divides, a portion of the flow being through the by-pass valve 31 and back through the conduit 40 to the reservoir tank and the remaining portion of the flow being back through the conduit 39 into internal annular grooves I31 and I36 in the valve body section 41 and from groove I through passage I39 in the valve body section 41 into passage I23 in the valve body section 48, into internal grooves I I1 and I I6, out from groove H6 past the spring-pressed ball I22 through the conduit 35 to the hydraulic motor 2I, back through conduit 36 into the annular grooves I20 and I I 9 in the valve body section 48, from groove II9 through passage I25 to the chamber 9| in the end cap 45, out through conduit 4|, and back through conduit to the reservoir tank 25.

It will be apparent that in this upward or for- Ward feed position of the lever 29, the amount of fluid by-passed through the al e 1 and consci sequently the fluid pressure applied to the hythe other motor is in a feed position. An'adjustable valve is provided in the hydraulic system to by -pass fluid from one of the hydraulic motors sons to control the fluid pressure applied thereto and consequently the actuation speed thereof. Provision is made in the control unit so that the 15 j by-pass valve is operable in one position of the hydraulic motor control but is inoperable in a reverse position of the control so that, for example, th forward speed of the motor maybe readily controlled but the motor can be quickly reversed and operated at full speed reverse regardless of the forward speed setting of the bypass valve.

In addition, a relief valve is incorporated In the controlunit to limit the fluid pressure applied to the hydraulic motors, which is highly advantageous when the torque or force which the elements or linkage to which the motors are connected can withstand, is limited. I

Further, when the controls are movedto the neutral positions thereof, fluid flow to the respective motors is blocked off so as to hydraulically lock the motors in position and so that operation of separate brakes is not necessary.

Thus, there is here provided a hydraulic drive system which is readily controlled to obtain desired operating conditions, which is readily constructed and assembled and which is reliable in of the present invention.

7 We claim as our invention:

1. For use in a-machine having a pair ofhydraulic motors actuating elements interrelated in operation, a hydraulic control system comprising: a multi-valved and passaged unit for connection to said hydraulic motors; means for supplying fluid under pressure to said unit; first manually operable means on said unit selectively movable between a feed position permitting fluid flow to one of said motors and a neutral position; second manually operable means on said control unit selectively movable between a feed position permitting fluid flow in one direction through the other of said motors and a reverse speed position permitting fluid flow in the reverse direction through said other of said motors; adjustable valve means by-passing fluid from said other of said motors in only the forward speed position of said second manually operabl means; fluid flow through said control unit to said other of said motors being blocked off in the feed position of said first manually operable means.

2. In a hydraulic system having a hydraulic motor, a supply of fluid under pressure and an adjustable valve for by-passing of fluid from said motor, a control unit comprising first and second passaged valve body sections, each section having a valve member movable therein, means connecting said by-pass valve to said first section, means connecting said hydraulic motor to the other of said sections, and a single control member connected to said valve members and selectively movable between a forward feed position in which 11' said by-pass valve is operable to control the fluid pressure applied to said motor and a reverse feed position in which said by-pass valve is blocked off and the full fluid pressure of the system applied to said motor.

3. In a hydraulic drive system including a pair of hydraulic motors, a fluid reservoir, a pump, an adjustable valve, a multi-valved and passaged control unit and conduits operably connecting the same, first manually operable means in said control unit for controlling one of said motors, and second manually operable means for controlling the other of said motors; said first manually operable means being selectively and adjustably movable between a feed position permitting application of fluid under pump pressure to said one motor and and blocking fluid flow to said other motor, a neutral position braking said one motor and permitting fluid flow to said other motor and a retract position permitting free movement of said one motor and permitting fluid flow to said other motor; and said second manually operable means being selectively movable between a forward feed position permitting application of fluid under pump pressure to said other motor and permitting by-passing of fluid under pump pressure from said other motor to said reservoir through said adjustable valve and a reverse feed position permitting flow of fluid under pump pressure through said other motor in a reverse direction and blocking ofi fluid flow through said adjustable by-pass valve.

4. In a hydraulic system having a hydraulic motor, a supply of fluid under pressure and a control valve for controlling fluid flow through said motor, a control unit comprising first and second passage valve body sections, each section having a valve member movable therein, means connecting said control valve to said first section, means connecting said hydraulic motor to the other of said sections, and a control member connected to said valve members and selectively movable between a forward feed position in which said control valve is operable to control the fluid 12 flow through said motor and a reverse feed position in which said control valve is blocked 05 and the full fluid pressure of the system applied to said motor.

5. In a hydraulic drive system including a pair of hydraulic motors, a fluid reservoir, a pump, an adjustable valve, 9. multi-valved and passaged control unit and conduits operably connecting the same, first manually operable means in said control unit for controlling one of said motors, and second manually operable means for controlling the other of said motors; said first manually operable means being selectively and adjustably movable between a feed position permitting application of fluid under pump pressure to said one motor and blocking fluid flow to said other motor, a neutral position braking said one motor and permitting fluid flow to said other motor and a retract position permitting free movement of said one motor and permitting fluid flow to said other motor; and said manually operable means being selectively movable between a forward teed position permitting flow of fluid under pump pressure through said other motor and through said ad justable valve to said reservoir and a reverse feed position permitting flow of fluid under pump pressure through said other motor to said reservoir in a reverse direction with said aifiustable valve inoperable to control fluid flow.

GUY BANISTER. LEONARD STEPHEN BURNS.

References Cited in the tile 01 this patent UNITED STATES PATENTS Number Name Date 2,160,596 LeBleu May 30, 1939 2,192,778 Stacy Mar. 5, 1940 2,247,140 Twyman June 24, 1941 2,247,141 Twyman June 24, 1941 2,489,435 Robinson Nov. 29, 1949 2,527,943 Lee Oct. 31, 1950 2,586,932 Gardiner et al Feb. 26, 1952 

